Indeed, with a 25-letters word there are 15,511,210,043,330,985,984,000,000 possible anagrams (25!)
So there is a very slight possibility that you exceed the expected 500ms computation time.
I don't know if you finished it since, because I personally solved this in python and not in ruby. But just in case, you can compute the word index directly from the letters in your word ;)

The Ruby version doesn't follow the Ruby conventions. Accessors shouldn't be named get and set

Check the Python solutions and you'll see. :)

Thanks, that array hack is a bit cleaner that mine.

The Array/Hash accessor [key] is very specific to those data structures. If I would read that code in a year, I'd have a hard time seeing at a glance what my Users or your Position is for. It just seemed to force a particular implementation and restricting freedom in solutions a little.

Doesn't really belong in the OOP category

This one shouldn't be in the OOP category at all

The forced in hash access for position[n] is really annoying, why not make it a method position(n). I basically had to add wrap Array in a class that sutracts 1 from the index.
And why test against the live site, a frozen copy of the leaderboard would work just as well.

I found the specs not very helpful when writing my code. BDD should guide me ideally, not confuse me.

A lot of the logic is also quite arbitrary and hard to follow.

Input will always be a non-negative integer.

What if someone enters a negative number? It should return 0 if something invalid is entered, but this would skip over your initial check in that case and possibly return a negative number.